2.0 Analysis 2.1 General The preliminary examination of the engine and the information provided by the pilot permitted the investigation to focus on the engine. However, the external equipment rack and its load were also examined. The analysis is limited to a discussion of the engine malfunction and the external equipment rack. 2.2 Blade Fracture The flat and darkened section of the fracture face of the failed second stage turbine blade is typical of a fatigue crack development. The remaining 35 per cent of the material of the blade suffered an instantaneous overload failure, as is indicated by its bright appearance. Analysis of the failed turbine blade did not indicate manufacturing or metallurgical problems within the blade material. It is suspected that the failure of this lone blade resulted from vibratory forces experienced within the gas path of the engine. The cracking and deformation of the nozzle circumference may have contributed to an abnormal gas flow and subsequent harmonic interference. 2.3 Power Loss When the turbine blade failed, it jammed between the following turbine blade and the TOT thermocouple. Simultaneously, the second turbine blade was bent at the tip, the thermocouple sheared off, and the mating surfaces of the gas producer rotor assembly and the third stage nozzle shield were deformed. The separated turbine blade section and thermocouple travelled back through the engine, damaging other blades and components. The resulting damage compromised the function of gas path components downstream of the second stage wheel, and resulted in an engine power loss. The power loss may not have been complete since the pilot observed a turbine outlet temperature reading of about 650 degrees Celsius after landing. 2.4 Warning Indications Throughout the occurrence, the aircraft had electrical power because the pilot was able to transmit on the radios. However, there was a complete absence of warning lights and horns throughout the occurrence, either in the air or on the ground, although they functioned normally after the occurrence. The position of the warning light circuit breaker was not determined immediately after the occurrence; however, it is likely that this circuit breaker was out and caused the warning circuit to be disabled. 2.5 Rack The mounting of the canoe on the rack prevented the opening of the doors on the right hand side of the helicopter. Loading in this manner was contrary to the approved flight manual supplement. 3.0 Conclusions 3.1 Findings The pilot was certified, trained, and qualified for the flight in accordance with existing regulations. The weight and centre of gravity were within the prescribed limits. Aircraft documentation indicated that the aircraft was certified, equipped, and maintained in accordance with existing regulations and approved procedures. The loading of the external rack prevented the opening of the right side doors and did not conform to the approved flight manual supplement. It is likely that the warning light circuit breaker was out and caused the warning circuit to be disabled. Circumferential cracking occurred adjacent to braze repairs on the second stage gas producer nozzle. The engine lost power when one blade of the second stage gas producer turbine wheel failed as a result of fatigue and caused internal damage to the turbine section of the engine. The fatigue of the blade was of a high-cycle nature, probably the result of engine- induced stresses/excitation. The source of the engine-induced stresses/excitation has not been determined. 3.2 Causes The engine lost power when internal damage to the turbine section was caused by a broken turbine blade. The blade failed in fatigue, likely as a result of engine-induced stresses/excitation. The source of the engine-induced stresses/excitation has not been determined. The Board has no aviation safety recommendations to issue at this time.4.0 Safety Action The Board has no aviation safety recommendations to issue at this time.